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Physics Colloquium - Friday, Feb. 27th, 2009, 4:00 P.M.

E300 Math/Science Center; Refreshments at 3:30 P.M. in Room E200

Mark Novotny
Department of Physics and Astronomy
HPCC Center for Computational Sciences
Mississippi State University

Far from Equilibrium Processes in Magnetic Nanoparticles and Thin Films: Experiments and Simulations: Hysteresis, Metastability, and a Dynamic Phase Transition

The concept of hysteresis in magnetic nanoparticles and thin magnetic films will be outlined, both the decades-old view and some of the required changes needed for ultra-thin magnetic layers at finite temperatures. One topic addressed will be how the hysteresis loop area depends on the frequency of the applied field. The existence of a Dynamic Phase Transition (DPT) in such hysteretic systems will be demonstrated. Results of large-scale simulations to determine the universality class of the DPT for highly-anisotropic thin film systems will be described. Experiments on ultra-thin multilayer magnetic structures comprised of [Co/Pt]_3 multilayers with a thickness of 0.4 nm will be discussed in detail, and evidence provided that a DPT has been seen experimentally in these magnetic systems.